Suppression of corrosion in ferrous alloy vessels in the treatment of hydrocarbons



Patented Sept. 21, 1948 ALLOY VESSELS IN HYDROCARBON THE TREATMENT OFElza Q. Camp, Goose Creek; Ten, assignor; by mcsne assignments,- toStandard Oil Development Company, Elizabeth, N. J a corporation ofDelaware, v No Drawing.

The present invention is directed {to a method 1 Application-August 19,1946, Serial No. 691,655

8 c aims. (01. ne 50') V optionally may be separatel introduced thereinwhereby hydrocarbons in contact with ayferrous alloy reaction vessel arethermally reacted under non-catalytic conditions and corrosion of thevessel and the deposition. of carbon thereon is stock through ferrousalloy tubes arranged in a turnace so that they would be maintained athigh temperatures and the carbon deposition and the corrosion heretoforementioned take place in the tubes of the furnace; this corrosion andcarbon deposition may be so rapid that the process is inoperable or atleast not commercially attractive. This rapid corrosion may beencountered even though the tubes are constructed of ferrous alloy, suchas the nickel and chromium alloyed with iron commonly known as 18-8alloy which, under many conditions, is very resistant to corresion.

It is an object of the present invention to react thermally ahydrocarbon feed stock under noncatalytic conditions While suppressingcorrosion of the reaction vessel and carbon deposition on the wallsthereof.

Other objects and advantages of the present invention will be seen fromthe following detailed description.

In accordance with the present invention, a hydrocarbon feed stock isthermally reacted in the vapor phase under non-catalytic conditions in areaction vessel with the hydrocarbon in contact with the ferrous alloyforming the interior wall of the vessel and corrosion of the reactionvessel and formation and deposition of carbon on the walls of thereaction vessel is suppressed by maintaining within the reaction zone asmall amount of an organic acid. In conducting the operation, it ispreferred to employ a petroleum fraction boiling within the range of 200to 400 F. as the feed stock and maintain the thermal reaction at atemperature within the range of 900 to1650 F. The organic acid ispreferably introduced into the feed stock passed into the reactionvessel but and may be maintained in the reaction zon in amountsextending" over a substantial range but usually 5% is the maximum amountemployed. Usually itwill be found that greatei eoncentra tion'sdonotproduce improved results" over the use or a 4% concentration ofsaid acid.

Th organic acidemployed for inhibiting the corrosion of the ferrousalloy vessel and the product and deposition of carbon Within thereaction mm preferably shouldhave a low. boiling range to insure that itremains in the vapor phase with the hydrocarbon i-eed stock. Preferredexamples of low molecular weight organic acid suitable for use in the;practice of the. present invention' are formic. acid,- acetic acidandpropionic acid; however, itmay at times befound desirable to employother acids or greater molecular weight, such as butyricand. valericacids. 7 .Theadvantages in the practice of the present invention will befurther shown by the following examples. In the first example conditionssimulating the prior art were employed and in the subsequent examplesthe method of the present invention was carried out.

Example I A petroleum fraction boiling within the range of 200 to 400 F.was heated to a temperature of 1450 F. and passed into vapor phasethrough a reaction vessel constructed of l88 chromiumnickel alloy steelfor an interval of 20 hours. The reaction was then terminated and theinterior of the reaction vessel examined. It was found that the 18-7-8alloy had been corroded at a rate of the order of 1 to 2 inchespenetration per year and was coated with a. copious quantity of carbon.

Example II A portion of the same feed stock used in Example I wasemployed and to the feed stock 3% by weight of formic acid was added andthe mix- 4 boxylic acid in the feed stock in the reaction zone tosuppress corrosion of said vessel.

4. A method in accordance with claim 3 in which the concentration ofcarboxylic acid in the feed stock is no greater. than 5%.

5. A method for conducting a vapor phase reaction including the steps ofcontacting a hydro- The advantage of the practice'of the presentinvention will be obvious. It will be seen that reactions heretoforeimpossible or commercially unattractive due to the rapid corrosion ofthe equipment and deposition of the carbon thereon may be conducted inaccordance with the'present invention and the corrosion of the reactionvessel suppressed and fouling of the vessel'by the depocarbon feed stockboiling within the range of 200 to 400. F. in the vapor phase and incontact with a ferrous alloy reaction vessel to a temperature within therange of 900 to 1650 F. to cause non=catalytic reaction of the feedstock and maintaining a carboxylic acid in the hydrosition of carbonthereon suppressed or eliminated.

I-Iaving fully described and illustrated the prac tice of the presentinvention, what I desire to claim as new and useful and to secure byLetters Patent is: a i v 1., A method for treating a hydrocarbon'feedstock comprising the steps of subjecting the feed stock in a vapor phasein contact with a ferrous alloy reaction vessel to a high temperature tocause non-catalytic reaction thereof and maintaining a carboxylic acidin the feed stock while it is in the reaction zoneto suppress corrosionof saidvessel. v

v 2. A method in accordance with claim 1 in which the concentration ofthe carboxylic acid in the feed stock is no greater than 5%.

3. A method for conducting a vapor phase reaction at elevatedtemperatures including the steps of subjecting a hydrocarbon feed stockto a temperature within the range of 900 to 1650 F. while it is incontact with a ferrous alloy reaction vessel to cause non-catalyticreaction thereof and maintaining a small amount of carcarbon feed stockin the reaction zone in aconcentration no greater than 5% to suppresscorrosion of said vessel.

6. A method in accordance with claim 5 in which the carboxylic acid isacetic acid.

'7. A method in accordance with claim 5 in which the carboxylic acid isformic acid.

8. A method in accordance with claim 5 in which the carboxylic acid ispropionic acid] ELZA Q. CAMP.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

